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  <title>Document</title>
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<body>
  <script>
    let arr = [1, 3, 5];
    arr.forEach(item => {
      // console.log(item);
      item++
      console.log(item);

    })
    console.log(arr);


    let arr1 = new Array(3) //设置了一个长度为3的数组
    arr1.fill().forEach(item => {
      console.log(item);  // undefined
    })


    let a = false, b = 'qwe'
    let str = a && b
    console.log(str);


  </script>
</body>

</html>